What
What = Qué?
What are we going to do today in class?
¿Qué vamos a hacer hoy en clase?
What time is it?
¿Qué hora es?
With what?
Con qué?
Where
Where = Donde ?
Where do you live?
¿Donde vives?
Why
Why…? = ¿por que…?
NB: For what reason
How
How = Como
How are you?
¿Como estas?
Who
Who = Quien?
Who has eaten my bacon sandwich?
Quien ha comido mi sandwich de beicon?
Delia is the person who ate your bacon sandwich.
With who/whom?
¿Con quien?
NB: In formal English who is used to replace a subject, while whom is used to replace an object
When
When = Cuando
When is our next English lesson?